In current telephony systems, approximately 60% of calls end in failure as a result of the intended recipient not being reached. The ability to be aware of whether an intended recipient is currently available, such as by means of a presence system, would eliminate time wasted in making fruitless calls to absent parties.
To date, presence and availability capabilities have been confined to instant messaging systems such as Microsoft Messenger and ICQ. Users are presented with availability information in the form of buddy lists. They may see which of their corespondents are available and attempt to send an instant message to them. The instant message system attempts delivery but there is no ability, such as is provided by call control in a telephony system, to forward the call to another party, take a message, etc. Thus, no solution has been provided in the prior art to the problem of missed calls due to party unavailability.
Presence and availability systems have not yet been applied to telephony because of the significant risk of conflict between call control policies associated with users or their devices and the availability information. For example, if a user has all of his calls blocked (e.g. Do Not Disturb (DND)) while still being marked as available in the presence system, confusion is bound to ensue as a result of the conflicting call control policies.